JEnterprise - Tutorials

Constants and Variables

Constants and Varibales are declared the same way as in Turbo Pascal:

const

  MyConstant = 100;

  MyOtherConst: real = 1.0;

var

  MyVar: integer;

  MySet: set of byte;

Note that (same as in Turbo Pascal) the variables are not initialized. You can however declare local typed constants:

procedure DoSomething;

const

  MyLocalConstant: real= 1.0;

begin

//...

end;

Ordinal types in Object Pascal:

Name	Range	Memory
ShortInt	-128..127	1 Byte
Byte	0..255	1 Byte
Integer	-32768..32768	4 Byte
Word	0..65535	2 Byte
Cardinal	0..65535	4 Byte
Longint	-2147483648..2147483647	4 Byte
Currency	+/-922337203685477.5807	4 Byte

Floating-point types in Object Pascal:

Name Range Precision Memory

Real 2.9*10^-39..1.7*10^38 11-12 digits 6 Byte

Single 1.5*10^-45..3.4*10^38 7-8 digits 4 Byte

Double 1.5*10^-324..1.7*10^308 15-16 digits 8 Byte

Extended 5*10^-4932..1.1*10^4932 19-20 digits 10 Byte

Comp -9.2*10^18..9.2*10^18 19-20 digits 8 Byte

Strings:

In 32bit Delphi (2.0 and 3.0) you also have long string instead of the old pascal string that were limited to 255 characters. The "Huge-String" compiler option is on by default. You can turn it off on the Compiler-tab in the project options.

Many Windows functions use the PChar type. It is a pointer to a string that does not have a length byte at the beginning. To indicate the end of the string the #0-byte is used. To convert a Pascal string to a PChar use PChar(MyString).

Language elements

Most parts of Object Pascal are identical with normal Pascal. Please refer to a pascal documentation for this.

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Name	Range	Precision	Memory
Real	2.910^-39..1.710^38	11-12 digits	6 Byte
Single	1.510^-45..3.410^38	7-8 digits	4 Byte
Double	1.510^-324..1.710^308	15-16 digits	8 Byte
Extended	510^-4932..1.110^4932	19-20 digits	10 Byte
Comp	-9.210^18..9.210^18	19-20 digits	8 Byte